DE 39 06 549 C2 describes an eccentric grinder that includes an electric drive motor in a housing, the drive shaft of which drives a support shaft of a grinding plate—on the underside of which grinding means are to be attached—via an eccentric support. Via the eccentric support of the support shaft, a superposed circular and rotary working motion of the grinding plate—and the grinding means attached thereto—is attained. In the working position, the grinding plate and the grinding means are pressed against the surface of the workpiece to be worked. Due to the support of the support shaft on the drive shaft, the grinding plate may rotate around its own axis only under certain conditions. When the eccentric grinder idles, however, i.e., when the grinding plate is lifted away from the workpiece to be worked, there is a risk that the grinding plate will begin to rotate at the rotational speed of the drive shaft, due to the bearing friction.
To limit the self-rotation of the grinding plate when the eccentric grinder idles, a friction brake is provided, which includes interacting frictional elements on the grinding plate and on the underside—which faces the grinding plate—of the housing of the eccentric grinder. With the friction brake, when the eccentric grinder idles, an outwardly lying rolling rim on the grinding plate may walk around an inwardly located, associated rolling rim on the housing, in which case self-rotation of the grinding disk is not prevented, but the rotational speed of the grinding disk may be reduced—as compared with the rotational speed of the motor—given that the outer rolling rim and the inner rolling rim are separated. Self-rotation is not entirely prevented in this embodiment, however.